Method and apparatus for texturizing yarn

ABSTRACT

METHOD AND APPARATUS FOR TEXTURING A MULTIFILAMENT YARN OR THREAD BY SUBJECTING THE YARN TO THE ACTION OF A FLUID JET WITH A NOZZLE OF OPEN DESIGN WHILE SIMULTANEOUSLY SUBJECTING THE YARN TO A FLUCTUATING LONGITUDINAL TENSION IN THE ZONE OF THE JET TREATMENT, THEREBY PERMITTING A MORE ACCURATE AND IMPROVED CONTROL OVER THE GAP LENGTHS OF THE TEXTURIZED YARN.

FREQUENCY Oct. 5, 1971 E. F. BOON 3,609,835

METHOD AND APPARATUS FOR TEXTURIZING YARN Filed July 23, 1969 GAP LENGTH ELECTRO MAGNETIC YARN BRAKE .I K E s l9 VAR L SPEED V GEA MEANS EDMUND F. BOON ATT'YS United States Patent 3,609,835 METHOD AND APPARATUS FOR TEXTURIZING YARN Edmund F. Boon, Wuppertal-Barmen, Germany, assignor to Glanzstoff AG, Wuppertal, Germany Filed July 23, 1969, Ser. No. 844,054 Claims priority, application Germany, July 24, 1968, P 17 60 957.3 Int. Cl. D02g 1/16 US. Cl. 281.4 19 Claims ABSTRACT OF THE DISCLOSURE Methods and apparatus are known for producing a texturized, tangled or intertwined effect in the individual filaments of multifilament yarns. Thus, apparatus is known which provides a bore, groove or the like as a yarn guide along whose longitudinal axis the yarn travels. As the yarn travels along guides such as these a jet of a fluid medium under pressure is blown onto it from one or more nozzles, with the result that the individual filaments are irregularly looped and/r intertwined. The nozzles may be differently arranged in various positions. The yarn or multifilament thread is guided through the jet under a tension which prevents it from slackening.

Another apparatus suitable for this texturizing of yarn is described in Canadian patent specification No. 554,150. In this case, the yarn is guided through a jet which issues from a nozzle and strikes a so-called resonance chamber situated opposite the nozzle opening.

By using such conventional methods and apparatus, it is thus possible to obtain a yarn which, despite a relatively small increase in volume, is intertwined or tangled in such a way that it can be further processed without any difficulties. Unfortunately, this advantage is offset by an excessive consumption of the fluid medium under pressure.

A measure of the texturization of the yarn, i.e. the amount of interlacing or entanglement, is the so-called gap length, sometimes referred to as the opening length. This gap length is defined as the distance by which a needle or pin inserted into the yarn perpendicularly to or radially of the yarn axis can be displaced axially of the yarn until the next entanglement or point of interlacing prevents further relative movement between the needle and the yarn. It will be apparent that the shorter the gap length, the greater the extent to which the individual filaments are entangled in the yarn. In cases where conventional methods and apparatus are used, it is noticeable that the gap lengths of yarns, which are to be wound or collected in the usual way following the texturizing treatment, differ greatly at the beginning and at the end of winding or collection. In addition, appreciable differences are evident in the gap length as between successive interlacing points.

Another disadvantage of conventional methods and apparatus for intertwining or interlacing the individual filaments of multifilament yarns by means of a pressurized fluid jet is that the gap lengths in the finished yarn differ greatly and, above all, cannot be predetermined or accurately controlled with regard to their average values. Thus, as a rule it is almost impossible to produce a texturized yarn package in which the average gap length,

3,609,835 Patented Oct. 5., 1971 as determined from the usually vastly different individual gap lengths, remains the same throughout the entire length of yarn being wound up into a package.

One object of the present invention is to make it possible to texturize multifilament yarns of widely variable denier in such a Way that the intervals between the entanglements or points of interlacing, i.e. the gap lengths, are kept the same or made to differ under predetermined and controlled conditions throughout the entire winding operation, i.e. in a manner comparable to the controlled conditions of producing a twisted yarn. It is also an object of the invention to provide a method or means to preadjust both the average gap length and to control any deviation from this average gap length to a large extent.

The invention is preferably carried out in combination with a yarn texturizing apparatus identical with or similar to that described in Canadian patent specification No. 554,150. Thus, the apparatus of this invention is readily adapted for use with conventional jet texturizing equipment. These and other objects and advantages of the invention will become more apparent from the following detailed specification.

The present invention essentially provides a method for producing a texturized multifilament yarn of predetermined average gap length, as defined hereinabove, in which the yarn to be treated is passed through a jet of a fluid medium, preferably air or steam, which is directed substantial- 1y perpendicularly to the linear path of travel of the yarn and thereafter flowing away or passing off freely from the texturizing zone, i.e. where the jet intersects the yarn path, and in which the yarn is simultaneous subjected to fluctuations in its linear tension as it passes through the texturizing zone, the frequency of the fluctuations in tension being given by the equation ice W 1 11- mm.

where n the number of cycles per minute of the fluctuations in tension, W=the rate of linear travel of the yarn in meters per minute and L the required average gap length of the texturized yarn in meters.

These fluctuations in yarn tension may follow one another at regular or irregular time intervals, depending upon whether it is desired to obtain a regular interval between the points of interlacing or a pattern of gap lengths which has a controlled irregularity. A preferred procedure, which is described in more detail hereinafter, produces a close similarity or uniformity between the individual gap lengths. In this case, the gap length is determined by a specific tension cycle and always corresponds with close approximation to the length of yarn which has passed through the blowing or texturizing zone, i.e. past the point at which the jet impinges on the yarn, during a single tension cycle. The gap length is thus mathematically determined by the relationship: L:W-z meters in which t is the duration of one tension cycle in minutes, while the remaining symbols are as defined above.

Tests conducted without subjecting the yarn to fluctuations in tension have shown that the gap lengths in the texturized yarn have individual values which as a rule differ extremely widely from the average gap length as determined statistically on the finished yarn product. In contrast, the individual gap lengths are substantially equal within narrow limits when regularly recurring fluctuations in tension have been applied to the yarn during the jet treatment. When these results are recorded in the form of a curve, there is a sharp maximum occurrence of that gap length which can be calculated from the frequency of the fluctuations in tension and the rate of travel of the yarn.

Basically, it is possible in accordance with the invention to follow three different procedures:

(a) The maximum variations around the calculated value of the gap length produces a statistical distribution of gap lengths similar to the Poisson distribution. This maximum variation is achieved by using jet pressures in the lower range of the limits specified and by employing lower and upper yarn tensions in the lower part of the particular ranges specified.

(b) In addition to a well defined maximum occurrence of the desired value calculated for the gap length, the yarn also exhibits nodules with lengths of up to a few centimeters. A distribution such as this is essentially obtained in those cases where W/n or W-t is less than about 0.02 meter. In addition, a distribution of gap lengths of this kind is obtained in those cases where the lower yarn tension in particular is reduced to approximately zero.

(c) The third possibility represents the preferred embodiment of the present invention wherein it is possible to obtain the expected or calculated gap length in the treated yarn with high accuracy and a high frequency of distribution or, where irregularity is required, to obtain a specific irregularity as between two or more calculated gap lengths with a high degree of accuracy. These results are achieved provided that certain requirements are satisfied, especially in regard to the pressure of the fluid jet and the yarn tension values.

Blowing or initial jet pressures of from 2.5 to 5 atms., preferably from 3.2 to 4.2 atms., are employed in those cases where air is used as the fluid jet medium. In cases where other fluid media such as steam are used, the initial pressures are corrected in a manner known to any competent expert in order to achieve the jet velocities as governed both by material and physical data to guarantee approximately equivalent jet impulses. The same applies as regards nozzles differing in form from those described.

For economical reasons, it is thus preferable to employ air as the fluid jet medium at approximately room temperature, e.g. at approximately 20 C., within the abovenoted pressure range. Under these conditions for instance the velocity of the jet as it leaves a nozzle furnished with a cylindrical bore or duct to impinge on the yarn amounts to the so-called critical velocity, e.g. about 315 meters/ second. Such velocity is of course conventional in this art to achieve a texturized yarn with a nozzle of open design and is merely provided to correlate the data set forth herein with reference to air so that one can readily substitute other gaseous or even liquid media as well as various nozzle designs which will yield the equivalent jet impulse. Thus, in addition to the preferred use of air, it is possible to employ other gases which are substantially inert to the yarn such as steam, nitrogen or even inert industrial waste gases. hWile it is most convenient to employ, e.g. approximately 2025 C., it is also feasible to use higher or lower temperatures so long as the yarn is not plasticized or deformed by exceptionally high temperatures.

The yarn tension preferably fluctuates between a lower range of from 0.02 to 0.18 gram/denier and an upper range of from 0.4 to 0.8 gram/ denier so as to achieve a narrow range of distribution of gap length close to the calculated value. The lower tension range is preferably between 0.04 and 0.15 gram/denier and the upper range preferably between 0.45 and 0.63 gram/denier.

Although the choice of the frequency of the fluctuations in yarn tension is not critical, technically expedient upper and lower limits arise out of the need for a practical working speed or rate of yarn travel on the one hand, and on the other hand, from the fact that the yarn must closely follow the deflecting movements and the measures producing the alternating change in tension between the high and low ranges without excessive outlay in terms of machinery. In addition, to this, allowance must be made for the fact that where W/n is smaller than about 002 meter, it is not possible to obtain strict consistency between the actual gap length and the calculated gap length. Instead, of the actual gap length falls short of the calculated gap length, a yarn of the type covered by the procedure (b) above is formed. For achieving a special yarn effect with recurring nodules of extremely short gap length, this procedure (b) can be employed.

Accordingly, favorable values for the frequency of the fluctuations in yarn tension lie at least above about 1500 cycles per minute, e.g. between about 2000 cycles/ min. and about 10,000 cycles/ min. and preferably between about 5,000 cycles/min. and about 8,500 cycles/min, i.e. corresponding to values between about 33 c.p.s. and about c.p.s., and preferably between about 83 c.p.s. and about 142 c.p.s.

Thus, important factors in the process of the invention include the take-off rate or speed of yarn travel, the frequency of the applied fluctuation in yarn tension, the upper and lower tension ranges, the nozzle dimensions and the initial jet pressure or the jet velocity and pressure at the mouth of the nozzle. In particular, it has been found that to obtain a sharp maximum frequency of occurrence of gap lengths corresponding to the calculated value, the ratio between minimum and maximum yarn tension and also the average value of the two tension ranges must be kept within relatively narrow limits. In this case it is essential to maintain a minimum tension, especially with a lower limit, as well as a maximum tension limited at both ends of the prescribed range, these tensions being dependent upon the denier of the yarn. Similarly, it is necessary to maintain a relatively narrow pressure range for the fluid jet medium during the texturizing treatment of the invention.

It has been found that the same end result can be obtained with the process according to the invention as with conventional processes, despite a lower consumption of air or other fluid medium. Another major advantage of the method according to the invention is that it is possible to obtain a texturized yarn which, unlike conventional yarns, has a regular distribution of nodules comparable to the regularity of a twisted yarn. Most importantly, when working under the preferred conditions of procedure (c) above, the calculated gap length is closely approximated throughout the entire texturizing treatment and can be adjusted as desired to provide a highly uniform degree of texturization.

The invention is illustrated by the following examples. In addition, apparatus suitable for carrying out the process according to the invention is discussed in considerably greater detail after these examples with reference to the accompanying drawings.

EXAMPLE 1 A polyester yarn having a yarn size of 68/24 denier was treated in a jet texturizing apparatus as described in Canadian patent specification No. 554,150 and indicated in FIG. 3 of the drawings with the following dimensions:

A pin is arranged 30 cm. in front of the blowing unit between two yarn guides arranged 15 cm. apart the pin being eccentrieally mounted with respect to the line of yarn travel on a disc rotatable about an axis perpendicularly to the direction of yarn travel, e.g. as indicated in FIG. 2 of the drawings. The pin serves to deflect the yarn periodically. The eccentric pin was arranged in such a way that the minimum yarn tension obtained was about 0.12 gram/denier and the maximum yarn tension obtained was about 0.52 ram/denier. The frequency of the fluctuation in yarn tension between these minimum and maximum values was adjusted to 7000 cycles/min. and the rate of yarn travel was 245 meters/min. The gap length was highly regular at 3.5 cm. which corresponds exactly to the calculated value:

meter) EXAMPLE 2 In an arrangement of exactly the same kind as that of Example 1, an eccentric is driven through an interference gear or so-called variable speed gearing means so as to produce deviations of 115% at an average frequency of 7000 cycles/ min. Examination of the gap lengths revealed an average gap length of 3.5 cm. with fluctuations in size corresponding to the percentage deviations in the deflection of tension frequency from the average value of 7,000 cycles/min. This example clearly shows that the method of the invention permits a very excellent control over the size of the gap lengths so as to be able to achieve practically any desired distribution of various gap lengths with uniform and reproducible results.

EXAMPLE 3 With otherwise the same arrangement and procedure as in Example 1, the blowing pressure or initial pressure of the air was varied between 3.5 and 3.9 atm. The gap lengths remained constant at 3.5 cm., although more distinct nodules were obtained as the blowing pressure increased.

EXAMPLE 4 With the same arrangement as that used in the preceding examples, at a constant frequency of 7,000 cycles/ min. and under a blowing pressure of 3.7 atm., both the lower and the upper tension values were varied by changing the effective eccentric diameter and also the position of the eccentric or the pin acting as the eccentric. Variations in the lower tension value between 0.74 and 0.13 gram/denier produced only a slight change in the effect, though the maximum frequency or occurrence of the calculated gap length became much more pronounced when the upper yarn tension was increased above about 0.45 gram/denier. The average gap length was constant at 3.5 cm.

EXAMPLE 5 The conditions of Example 3 were modified by increasing the upper yarn tension in stages. It was found that when the maximum yarn tension was increased beyond 0.59-0.60 gram/denier and the lower yarn tension was simultaneously lowered to below .074 gram/denier, neither a regular distribution of the gap lengths nor one changing with the tension frequency occurred in a well defined form. At a blowing pressure of from 3.5 to about 3.7 atm., there was a wider variation in the gap lengths with a maximum occurrence at around 3.5 cm. i.e. corresponding to procedure (a) above. At a blowing pressure of from about 3.7 to 3.9 atms., there was a pronounced peak at a gap length of 3.5 cm. although very short as well as relatively long Opening lengths were also noticed, i.e. corresponding to procedure (b) above.

EXAMPLE 6 Under otherwise the same conditions as in Example 3, a yarn tension of 0 and 0.66 gram/denier was alternated periodically. The distribution of gap lengths according to procedure (a) was obtained at blowing pressures of from 3.5 to 3.7 atm., while the distribution according to procedure (b) was obtained at blowing pressures of from 3.8 to about 4.0 atms.

EXAMPLE 7 Under otherwise the same conditions as in Example 1, the rate of yarn travel was reduced in stages. Up to a yarn travel rate of 140 meters/min. (L= 40/7000=0.02 meter),

the gap length corresponded exactly to the calculated conditions. When the yarn travel rate was further decreased the distribution changed to that shown in the case of procedure (b).

The invention as set forth in the preceding examples and with reference to suitable apparatus will now be further described with reference to the accompanying drawings, wherein:

FIG. 1 illustrates different distribution curves for the opening or gap length depending upon the particular technique or procedure used, the frequency of occurrence of each particular gap length being plotted against the gap length;

FIG. 2 is a schematic illustration of a combination of apparatus for carrying out the process according to the invention;

FIG. 3 illustrates in partly schematic form a known type of jet nozzle and resonance chamber suitable for carrying out the process according to the invention;

FIG. 4 is a partly schematic perspective view of an electromagnetic yarn brake suitable for achieving a fluctuating yarn tension; and

FIG. 5 is a schematic representation of drive means linked with an eccentric deflecting cam by means of a variable gearing means to produce specific deviations from an average frequency of fluctuation in tension.

In FIG. 1, the curve 1 shows the frequency distribution of the gap lengths in the treatment of a yarn in following procedure (a) above. Curve 2 shows the distribution of the gap lengths in the case of a yarn treated in accordance with the preferred embodiment of the invention, i.e. case (c) above. Curve 3 shows the frequency distribution of the gap lengths formed in cases where the procedure resulted in case (b). As can be clearly seen, the maxima lie at the gap length as calculated from the formula L=W-t.

FIG. 2 schematically illustrates the more important elements of an apparatus for carrying out the process according to the invention. A multifilament yarn 4 being texturized passes through the yarn guides 5 and 6 which are disposed respectively in front of and behind an eccentric disc 7 which carries a deflector pin 8. The nozzle 9 is of open design with a suitable embodiment thereof being shown by way of example in FIG. 3. Arranged respectively in front of and behind the jet or texturizing zone, there are placed yarn guides 10 and 11 by which the yarn is held in a normally linear path through the jet. How'- ever, it will be recognized that the yarn tends to fluctuate from side to side under the influence of the jet, particularly with a resonance chamber aligned on the same axis with the jet nozzle. Any form of blowing unit can be used which enables the fluid medium to flow off relatively freely from the texturizing zone.

The yarn 4 travels from a delivery means such as a pair of nip rolls 12 and 13 arranged in front of the yarn guide 5, through the yarn guide 5, and over the deflector pin 8 as an eccentric yarn contacting element or over the circumferential yarn contacting surface of the disc 7. A variation in yarn tension is thus produced as between the deflector pin 8 and the disc 7 as the yarn passes through the yarn guide 6 of the blowing nozzle 9 and then through another delivery means such as rolls 14 and 15 to a conventional winding or take-up mechanism (not shown).

The axis of rotation of the eccentric disc 7 is preferably arranged in such a way that it can be displaced perpendicularly of the direction of yarn travel, the axis remaining parallel to its original position. In this way the extent to which the yarn is deflected can be controlled. In place of or in addition to this adjustment of the disc axis, the pin 8 on the disc 7 may also be radially adjustable, or pins of different sizes can be used. It will be evident that one yarn tension fluctuation cycle or period corresponds to one revolution of the eccentric disc 7 when using a single deflector pin 8. Instead of one pin 8, two or more pins 8' may be arranged at regular intervals around the periphery of the eccentric disc, i.e. as indicated in dotted lines. The upper limit to the number of pins is governed by the requirement that no pin 8' must touch the yarn until the preceding pin has ceased to be in contact with the yarn.

Instead of the eccentric referred to in connection with the rotatable disc 7, any other known adjustable tensioning means may be used or adapted to produce the fluctuations in yarn tension. For example, an electromagnetic yarn brake as illustrated in FIG. 4, which can be rapidly switched on and off to produce the required frequency, is also especially suitable in providing a smooth transition back and forth between the upper and lower values of tension. A vibrator of adjustable frequency may also be used. It is not essential for the fluctuations in yarn tension to provide a sine Wave or curve when plotting the amount of tension against time, and in fact, it is preferable to maintain the lower tension on the yarn over a large proportion of each cycle with only a relatively brief interruption during which the tension is quickly increased to the prescribed higher tension. The beneficial results of the invention in all cases appears to arise primarily from the rapid and regularly repeated fluctuation in tension between the low and high ranges as prescribed herein. On the other hand, this does not rule out the possibility of achieving special texturizing effects where an irregular pattern of interlacing or a. variation of gap lengths is produced under controlled and reproducible conditions.

The embodiment shown in FIG. 3 is an exemplary form of a suitable jet nozzle which has a nozzle body 16 with a jet channel or blowing duct 17 and, opposite this duct, a second body 18 in which a resonance or compression chamber 19 is arranged. A texturizing zone is defined by the common axis of the blowing duct 17 and the compression chamber 19. Two yarn guides and 11, each of which is preferably in the form of a narrow eye or small tube, are arranged just in front of and just behind the texturizing zone in such a way that they tend to keep the yarn 4 passing precisely through the jet of air or other fluid medium. The jet nozzles that may be used for carry ing out the process according to the present invention are by no means limited to this particular embodiment as shown in FIG. 3.

In fact it is possible to use any type of nozzle that enables the fluid medium to flow or pass off substantially freely from the jet or texturizing zone. For example, the resonance or compression chamber 19 may be omitted entirely or may be replaced by a flat plate or any other type of obstacle to the jet flow. The only requirement that must be satisfied is that the fluid medium should be able to flow off relatively freely from the treatment zone, preferably not at all or only partly in the direction of the general yarn axis. The types of jet nozzles or blowing nn its having this characteristic freedom of flow are referred to in the present context as nozzles of open design. Thus, not only does the jet impinge substantially or at least approximately perpendicularly to the yarn axis, but it is also permitted to dissipate as freely as possible away from the point of treatment or from the resonance zone established by means of an oppositely disposed resonance chamber. Poorer results are achieved if this dissipation of the jet stream is channeled in a specific direction, especially if directed solely along the axis of the yarn.

The means used to generate the fluctuations in yarn tension must be arranged between the delivery means 12, 13 and 14, but may be disposed on either side of the nozzle 9. In other words, the yarn tensioning means may be arranged in front of or behind the nozzle 9, as seen in the direction of yarn travel.

While certain special effects can be achieved simply by adjusting the initial pressure of the jet medium and/or working outside of the prescribed ranges of upper and lower yarn. tension, dill irregular but controlled pattern of gap lengths is most easily achieved by working under the preferred conditions of the invention while changing only the frequency of the tension fluctuations according to a prescribed pattern. Thus, as indicated schematically in FIG. 4-, the two lower pins 20 and 21 are held in a stationary position while the upper pin 22 is caused to fluctuate in a plane perpendicular to the axis of the yarn 4 as indicated by the double-headed arrow, e.g. by means of a solenoid or similar electromagnetic means which can be turned on and off to produce reciprocating movement of the pin 22 at the required frequencies. To achieve an irregular pattern of frequencies, any suitable programmed switching means can be employed to vary the frequency in a predetermined manner.

Likewise, as indicated in FIG. 5, the eccentric disc 7 of FIG. 2 can be driven by a variable speed motor 23 to establish a specific desired frequency of fluctuation in yarn tension while arranging a variable speed gearing means 24 between the motor 23 and the disc 7 so as to produce a variation in the fluctuation frequency, e.g. both above and/or below the average or prefixed frequency established by the motor 23.

Other similar arrangements can be readily provided by a skilled mechanic in order to program variations in the frequency of tension fluctuation. In most cases, one can readily achieve a variation of up to i25% of the average frequency. Rapid changes in the frequency within this interference width or frequency band of up to i25%, preferably between about :5% and results in a relatively uniform distribution of different gap length with the yarn still exhibiting an average gap length as calculated from the average frequency. On the other hand, it is also possible to achieve a more gradual increase or decrease in the gap lengths over a length of yarn, e.g. simply by connecting the disc 7 directly to the variable speed motor 23 and gradually decreasing or increasing the speed of the motor.

These and other modifications of the method or apparatus of the invention can be readily adapted without departing from the basic concept of the invention as explained hereinabove.

The invention is hereby claimed as follows:

1. In a method of texturizing a rnultifilament yarn by passing the yarn through a jet of a fluid medium directed substantially perpendicularly to the linear path of travel of the yarn with said fluid medium passing off substan tially freely from the texturizing zone, the improvement which comprises: simultaneously subjecting the yarn to a fluctuating linear tension as it passes through said texturizing zone, said fluctuations in tension occurring between an upper value falling in the range of about 0.4 to 0.8 gram/denier and a lower value falling in the range of about 0.02 to 0.18 gram/ denier with the frequency of the fluctuations in tension being defined by the equation:

1t: min

where n is the number of cycles of the fluctuations in tension per minute, W is the rate of linear travel of the yarn in meters per minute and L is the required average gap length of the texturized yarn in meters.

2. A method as claimed in claim 1 wherein the fluid jet is produced under a pressure of about 2.5 to 5 atmospheres with reference to air as the fluid medium.

3. A method as claimed in claim 2 wherein air is used as the fluid medium at a temperature of about 20 C. to 25 C.

4. A method as claimed in claim 3 wherein the air pressure for producing the jet is between about 3.2 and 4.2 atmospheres.

5. A method as claimed in claim 1 wherein the frequency of said fluctuations in yarn tension is from about 2,000 to 10,000 cycles per minute.

6. A method as claimed in claim 1 wherein the frequency of said fluctuations in yarn tension is from about 5,000 to 8,500 cycles per minute.

7. A method as claimed in claim. 1 wherein the frequency of said fluctuations in yarn tension is from about 0.45 to 0.63 gram/denier and a lower value of about 0.04 to 0.15 gram/denier.

8. A method as claimed in claim 7 wherein the frequency of said fluctuations in yarn tension is from about 2,000 to 10,000 cycles per minute.

9. A method as claimed in claim 7 wherein the frequency of said fluctuations in yarn tension is from about 5,000 to 8,500 cycles per minute.

10. A method as claimed in claim 1 wherein air is used as the fluid medium at an initial pressure of 2.5 to 5 atmospheres and the yarn tension is fluctuated at a frequency of about 2,000 to 10,000 cycles per minute between an upper tension of 0.4 to 0.8 gram/denier and a lower tension of 0.02. to 0.18 gram/ denier.

11. Apparatus for producing a texturized multifilament yarn having a predetermined average gap length which comprises in combination:

a texturizing jet nozzle of open design to direct a jet of fluid medium onto said multifilament yarn with means to guide said yarn in a normally linear path through said jet while the fluid medium passes off substantially freely from its point of directed jet contact with said yarn;

means to conduct the yarn at a predetermined linear speed of travel through said jet; and

means to subject said yarn to regularly programmed fluctuations in linear yarn tension at the zone of jet contact with the yarn, the frequency of said fluctuations generated by said means being given by the equation 11 min wherein n is the number of cycles per minute of the fluctuations in yarn tension, W is the rate of linear travel of the yarn in meters per minute and L is the required average gap length in meters.

12. Apparatus as claimed in claim 11 wherein said texturizing jet nozzle is directed substantially perpendicularly to the linear path of the yarn and is so arranged together with said yarn guide means to permit the fluid medium to flow freely away from the zone of jet contact with the yarn in directions predominately other than the path of the yarn.

13. Apparatus as claimed in claim 11 wherein said texturizing jet nozzle is combined with a resonance cham- 10 her opposite to and on a common axis with said nozzle and adapted to receive said jet of fluid medium to create a turbulent texturizing zone therebetween.

14. Apparatus as claimed in claim 11 wherein two yarn conducting means are arranged on either side of said nozzle and said means for generating the fluctuations in yarn tension is arranged between one of said conducting means and said nozzle.

15. Apparatus as claimed in claim 14 wherein said means for generating the fluctuations in yarn tension is arranged between the first of said yarn conducting means and the nozzle as seen in the direction of yarn travel.

16. Apparatus as claimed in claim 11 wherein said means for generating the fluctuations in yarn tension is an electromagnetic yarn brake.

17. Apparatus as claimed in claim 11 wherein said means for generating the fluctuations in yarn tension is a yarn deflecting means including a rotatable eccentric driven by a variable speed motor.

18. Apparatus as claimed in claim. 11 including additional means to program variations in the frequency n of said yarn tension fluctuations in an amount of up to i-2S% of the average frequency established by said means for generating said fluctuations.

19. Apparatus as claimed in claim 11 including additional means to program variations in the frequency n of said yarn tension fluctuations in an amount of from about :5% up to about il5% of the average frequency established by said means for generating said fluctuations.

References Cited UNITED STATES PATENTS 2,874,445 2/1959 Griset 28-1.4 2,931,090 4/1960 Field 2'81.4 3,083,522 4/1963 Rokowski et al. 57-34- 3,425,108 2/1969 Cerutti et a1. 281.4

FOREIGN PATENTS 554,150 3/1958 Canada 28-7212 LOUIS K. RJMRODT, Primary Examiner U.S. Cl. X.R. 28-7212 

